American Carla Stefaniak had been vacationing with her sister-in-law in Costa Rica.
CNN —  

Costa Rican authorities believe a partially decomposed body found Monday is Carla Stefaniak, a 36-year-old US citizen who was reported missing last week, said Walter Espinoza, of Costa Rica’s Judicial Investigation Department.

“Everything points to this being her body,” Espinoza said. “However, we still require more technical, more precise, and more scientific determinations.”

Police detained a security guard from the Airbnb where Stefaniak was staying after inconsistencies in his statements, Espinoza said. The man, who is a Nicaraguan national, is being held in jail because he is a flight risk.

The man was staying at the apartment next to Stefaniak’s rental, according to the police agency.

A Facebook page that is being updated by a family friend says relatives have not identified the remains.

“The family has yet to see the body and they were in the process of securing dental records for the examiners!” the post on Finding Carla says. “We don’t know why the media is announcing the identity of the body or what Costa Rica officials are trying to do by not allowing the family to view the remains BEFORE announcing anything.

Missing for a week

Earlier, police said they had discovered a female body “in a state of decomposition” near where Stefaniak was last seen. They added later that the body was found about 300 meters away from the apartment complex.

Authorities found the decomposed body around noon Monday in a wooded area of San Antonio de Escazu, Espinoza said.

Stefaniak, 36, was reported missing by her family in Florida last week. Relatives raised the alarm after she stopped texting and telephoning home and was not on her return flight from Costa Rica, where she had been vacationing.

Authorities also had found stains inside the apartment where Stefaniak was staying, “which are compatible with blood and which will be submitted to further investigation and comparison,” he said.

Birthday celebration turns to mystery

April Burton, her sister-in-law, told CNN the two had gone to Costa Rica to celebrate Stefaniak’s birthday and had traveled together for six days, staying in beach towns outside San Jose.

Burton told CNN the two were in Costa Rica to celebrate Stefaniak’s birthday, and had traveled together for six days.

Stefaniak is friendly, bubbly and loves to travel, her sister-in-law said.

A day before she went missing, Stefaniak dropped Burton at the airport and returned their rental car.

Stefaniak and Burton had been texting each other via WhatsApp, Burton said. Then, the messages stopped.

And Wednesday, Stefaniak did not board her flight home.

“That’s when we knew that something’s not right,” she said. “You never want to think the worst, but that’s where your mind goes to automatically. … For almost six days to go by and no contact, she would have to have been abducted.”

Unusual behavior

The complex where Stefaniak had been stayed is temporarily closed, a lawyer for the site told CNN affiliate WFTS.

US State Department officials were aware of the reports of a missing American in Costa Rica, a representative told CNN.

“When a US citizen is missing, we work closely with local authorities as they carry out their search efforts. We stand ready to provide all possible assistance to US citizens in need and to their families. Due to privacy considerations, we have no further comment,” the representative said.

Speaking Monday to HLN, CNN’s sister network, Burton urged anyone who might have information about her sister-in-law’s whereabouts to come forward.

“She’s a great person. So friendly, so bubbly, loves to travel, loves fashion, loves social media,” she said.

CNN affiliate WFTS reported that a lawyer for the place where Stefaniak was staying said the facility is temporarily closed.

“The owners are fully cooperating with the authorities in the investigation and we hope that once the facts are determined, the perpetrator is brought to justice,” the attorney, who was not identified, told the Tampa station.

CORRECTION: This story has been updated to correct the day the body was found and to correct the timeline of Stefaniak’s last communication and scheduled travel day.

CNN’s Lynn Franco, Jamiel Lynch, AnneClaire Stapleton, AJ Davis, Jennifer Hansler and Duarte Mendonca contributed to this report.